Discovery, TESS Characterization, and Modeling of Pulsations in the Extremely Low-mass White Dwarf GD 278
Discovery, TESS Characterization, and Modeling of Pulsations in the Extremely Low-mass White Dwarf GD 278
复制标题
DOI：
10.3847/1538-4357/ac2d28
复制
发表时间：
2021-10
期刊：
影响因子：
--
通讯作者：
Isaac D. Lopez;J. Hermes;L. M. Calcaferro;K. Bell;Adam Samuels;Z. Vanderbosch;A. Córsico;A. Istrate
中科院分区：
文献类型：
--
作者：
Isaac D. Lopez;J. Hermes;L. M. Calcaferro;K. Bell;Adam Samuels;Z. Vanderbosch;A. Córsico;A. Istrate
我们报告通过地基和空基光度测量在极低质量（ELM）（可能是氦核白矮星 GD 278）中发现脉动。 GD 278 由第 18 区的凌日系外行星勘测卫星 (TESS) 以 2 分钟的节奏观测了大约 24 天。 TESS 数据揭示了 2447 秒到 6729 秒之间至少有 19 个重要周期性，其中之一是在白矮星中检测到的最长脉动周期。先前的光谱分析发现，这颗白矮星处于 4.61 小时的轨道上，有一个看不见的 >0.4 M ⊙ 伴星，T eff = 9230 ± 100 K 和 logg=6.627±0.056 ，对应的质量为 0.191 ± 0.013 M ⊙ 。来自旋转分裂的 TESS 脉动频率模式似乎揭示了大约 10 小时的恒星旋转周期，使 GD 278 成为第一颗具有测量旋转速率的 ELM 白矮星。这些模式为我们星震拟合的模式识别提供了信息，不幸的是，这并没有揭示全局最佳拟合解决方案。星震学揭示了两种主要解，它们与这颗 ELM 白矮星的光谱参数大致一致，但氢层质量却截然不同；未来的地震拟合可以通过使用恒星视差进一步改进。 GD 278 是目前已知的第十颗脉动 ELM 白矮星；它只是已知的第五个短周期双星系统，但却是第一个具有扩展的、基于空间的光度测量的双星系统。
We report the discovery of pulsations in the extremely low-mass (ELM), likely helium-core white dwarf GD 278 via ground- and space-based photometry. GD 278 was observed by the Transiting Exoplanet Survey Satellite (TESS) in Sector 18 at a 2 minute cadence for roughly 24 days. The TESS data reveal at least 19 significant periodicities between 2447 and 6729 s, one of which is the longest pulsation period ever detected in a white dwarf. Previous spectroscopy found that this white dwarf is in a 4.61 hr orbit with an unseen >0.4 M ⊙ companion and has T eff = 9230 ± 100 K and logg=6.627±0.056 , which corresponds to a mass of 0.191 ± 0.013 M ⊙. Patterns in the TESS pulsation frequencies from rotational splittings appear to reveal a stellar rotation period of roughly 10 hr, making GD 278 the first ELM white dwarf with a measured rotation rate. The patterns inform our mode identification for asteroseismic fits, which, unfortunately, do not reveal a global best-fit solution. Asteroseismology reveals two main solutions roughly consistent with the spectroscopic parameters of this ELM white dwarf, but with vastly different hydrogen-layer masses; future seismic fits could be further improved by using the stellar parallax. GD 278 is now the tenth known pulsating ELM white dwarf; it is only the fifth known to be in a short-period binary, but is the first with extended, space-based photometry.